1. Field of the Invention
This invention relates to ultrasonic non-contact sensing devices for measuring distances from a source as a measure of the time it takes for a sound wave to bounce off an object whose distance is being measured and returned to the source.
2. Utilization
In a number of situations it is necessary that a distance measurement to an object be made without actually contacting the object. Such situation may further require that the object distance be constantly monitored. Such non-contact monitoring may be required to prevent damage to a distance measuring sensor or to prevent damage or disruption to the object or surface being measured or monitored. Also, the presence of a hazardous environment may preclude the use of direct contact sensing or distance measuring, such as in the monitoring of a liquid level in a vat of a corrosive or caustic solution. With non-contact sensing, as actual contact is not required and, the distance measuring sensor can be physically isolated from the object, precluding damage to the sensor or to the surface of the object being monitored. Additionally, as measurements are made from a distance, the sensor and measurement device may be conveniently located outside of hazardous environments thereby preserving the integrity, accuracy, and reliability of the measuring equipment.
3. Prior Art
Ultrasonic sensors and apparatus are well known and, like the present invention, a number provide a capability for remote distance measuring. Examples of some of such earlier devices are shown in patents to Austin, et al., U.S. Pat. No. 4,170,765; Massa, U.S. Pat. No. 4,210,969; Newman, U.S. Pat. No. 4,584,676; Farmer, et al., U.S. Pat. No. 4,572,253; Soltz, U.S. Pat. No. 4,518,997; Schurr, U.S. Pat. No. 4,101,865; Carlin, et al., U.S. Pat. No. 4,487,065; a Soviet Union Patent No. 0,563,320; and a patent to Combs, et al., U.S. Pat. No. 4,221,004. Which Combs patent also provides for a voltage level adjustment to an amplifier. Neither the Combs patent nor any of the above, however, provide an instrument with versatility and reliability of the present invention that provides a doubling to tripling in sensing range over other known ultrasonic instrument of the same size sensor and power range.
A prior patent application owned by the owner of the present invention, Ser. No. 07/187,986, now abandoned, sets out an earlier ultrasonic distance measuring device, that was made and sold, that the present invention improves upon. The above-cited prior art references and others were cited against allowance of which application Ser. No. 07/187,986.